Sail construction



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SAIL CONSTRUCTION 2 Sheets-Sheet l Filed April so, 1948 f f f INVENTORS IIS J//fbffyey March 7, 1950 J. A. MAURER ET AL. 294999598 SAIL CONSTRUCTION Filed April 30, 1948 2 Shemes--ShezawI 2 IN V EN TOR)` MMMQM Patented Mar. 7, 1950 SAIL CONSTRUCTION James A. Maurer, Whitefish Bay, and Walter R. Lindemann, Milwaukee, Wis.

Application April 30, 1948,.Serial No. 24,196`

' Claims.

This invention relates to sails for vessels and other objects intended to be propelled by the wind, and it resides more specifically in an improved constructon for sails of the fore and aft type in which the principal propelling portion of the sail assumes, with substantially no distortion of the mesh of .the canvas, an aerodynamically desirable curvature.

One object of this invention is to provide a sail, the construction of which is such that the same assumes under wind action a predetermined contour of aerodynamic advantage.

Another object of this invention is to provide a sail which assumes an aerodynamically advantageous contour under wind action, which contour remains to a greater degree independent of the strength of the wind.

Another object of this invention is to provide a sail, the construction of which is such that the same may under wind action assume an aerodynamically desirable contour without substantial distortion of the mesh of the canvas.

Another object of this invention is to provide a sail, the construction of which is such that the same will assume an aerodynamically desirable contour when rst hoisted without need for breaking in treatment.

Another object of Athis invention is to provide a sail,l the construction of which is such that loading due to wind action is without distorting effect upon the mesh of the canvas, thus permitting the sail to maintain a desired shape throughout thev useful life of the canvas and so long as the same retains suflicient strength to resist forces applied by wind action.

The above and other objects and advantages of this invention will become apparent from thev description following which is set forth by reference to the accompanying drawings, forming a Fig. 4 is a diagrammatic plan View in Section of the sail shown in Fig. 1 "viewed through the, plane 4-4 there indicated; A

Fig. 5 is a diagrammatic plan view in section of the sail shown in Fig. 1 viewed through vthe plane 5-5 there indicated;

Fig. 6 is a diagrammatic plan View in section of the sail shown in Fig. 1 viewed through .theI plane 6 6 there indicated;

Fig. 7 is a diagrammatic view in elevation and in section on a reduced scale of the sail shown in Fig. l viewed through the ,plane 1 -.1 there indicated; and

Fig. 8 is a side view in elevation of another form of sail constructed in accordance with this invention.

On practically all points of sailing otherwise than when a vessel is running directly before the.

wind the propulsive force derived from the sails,

is dependent in considerable measure upon the preservation in the sails of an aerofoil section. I-Ieretofore, it has been the practice, particularly in the case of sails of the fore and aft type, to` cut the same so as to provide draftj which when the sail is 'hoisted and drawing, makes available a degree of baggyness in the canvas.,r which under wind action, and upon distortiolflv` of the mesh of the canvasr becomes converted into a contour having an aerofoil section. A very high degree of skill and understanding on the part of the sail cutter is. required toY determine the shape and quantity of draft which will give the sail the desired contour when in use. An equivalent degree of skill and under standing on. the part of the user ofthe sail must part hereof, in which there is set forth by way of illustration and not of limitation, forms in which sails may be constructed in accordance with this invention.

In the drawings:

Fig. 1 is a side view in elevation "of va mainsail of the jib headed type constructed in accordance with this invention;

Fig. 2 is a fragmentary view in` perspective viewed from the after end of a boom upon which, the sail shown in Fig. 1 is extended;

Fig. 3 is a developed diagrammatic side view in elevation in fragmentary form of the main propelling portion and the camber Aforming portion of the sail shown in Fig. 1 unattened condition prior to closing of the seam between the same;

be exercised and availed of in first setting and' breaking in the sail. The roping of the sail as well as the canvas must be stretched and distorted in a particular fashion in order 'to carryL out the intent of the sail cutter.

Even where such skill and understanding is` exercised, both on the, part of the, person who. cuts the sail and on the. part of the person who rst hoists and breaks it in, 'the desired shape is rarely attained and even when attained, is only briefly preserved since the distortion of the mesh of the canvasy continues while` the sail is in use bringing about sooner or later a shape unfavorable to fullv utilization of the propulsive forceof the wind.

To overcome the 'aforesaid difficulties aV sail may be constructed in accordance with this-'invention, for example, as Villustrated Vin Fig. 1 where the invention is shown embodiedin afore and aft mainsailof ythe jib headed type. The sail shown in Fig. 1 is made up of ama'infpxfopulsive portion I bounded on its after side by the leech 2, on its forward side by the lui 3 (cut without draft), and on its lower side by an arcuate seam 4. The propulsive portion I is sewn from a plurality of cloths as indicated, arranged transversely of the pull of the halyard attached to the headboard 5. The propulsive portion I also is furnished with the usual batten pockets 6 as shown.

Joined to the lower edge of the propulsive portion I at the seam 4 is an obliquely positioned camber forming portion 'I which acts to provide the foot 8 for the sail. The sail is roped in the usual fashion throughout the length of the luff 3 and the foot 8 by means of the bolt rope 9 sewn in place as shown. Secured to the tack of the sail with the aid of reinforcing' I Il is a tack grommet II. In similar fashion a clew grommet I2 is secured to the clew with the aid of reinforcing I3. Sail track slides I4 aresewn in place through thevlength of the bolt rope at the luff and `foot as indicated. y

The camber forming portion I is preferably cut without draft or curvature in the foot 8 and is provided as shown in Fig. 3 with a curvature 4 at its upper edge. The propulsive portion I of the sail in turn is cut with its lower margin 4 curved to meet the upper margin 4" of the camber forming portion l when the propulsive portion I is shaped to the aerodynamic contour above referred to. The simple, conical iiexing of propulsive portion I, which is all that is required to bring the same to a meeting with the upper edge of camber forming portion 'I introduces no distortion into the mesh of the canvas contained in either the portion I or the portion 1. By reason of the conliguration of the portions I and 1 prior tol joining at the seam 4, the sail when hoisted and subjected to wind action naturally assumes a shape approximately as indicated in Fig. 2 and this shape, as explained above, is one in whichV no substantial distortion of the mesh of the canvas is required.

, As shown in Fig. 4, at a point near to the foot 8, the sail naturally assumes, under wind action, a condition of slight curvature close to lui 3, formed by the curvature of `the propulsive portion I. Throughout the extent of the camber forming portion '1, however, little or no curvature in the canvas is evident while as the leech 2 is approached, the propulsive portion I again shows a slight curvature. At a point shortly above the level of the camber forming portion 1 the propulsive portion I carries throughout, from the luif 3 to the leech 2, a curvature aerodynamically favorable to maximum propulsive effect, and this condition prevails throughout the height of thev sail to the level of the headboard, for example, as indicated in Fig. 6.

As above stated and as indicated in Figs. 2 and 7 the camber forming portion 'I is obliquely disposed at a pre-determined angle to the position assumed by the main propulsive portion of the sail I. |I'his angle is designated 24 in Fig. 2. By so positioning the camber forming portion 'I the sail assumes readily and naturally the contour intended under wind action, both heavy and light. For a general purpose sail, the angle 24 preferably will be between 145 degrees and 155 degrees, although the advantages of this invention may be obtained for special purposes where the angle thus measured is as small as 100 degrees or as large as 170 degrees. It will be understood that for any angle of obliquity chosen that the curvature 4 of the the purpose of this invention to prescribe a particular aerofoil section to be employed in the construction of a sail. It is the purpose rather to provide means by which a desired and selected camber or aerofoil section may be controllably achieved and maintained without breaking in of the sail and without the progressive alteration in camber which is attentant upon sail contours achieved through distortion of the mesh of the canvas.

This invention ndsl useful application not only in the case of sails extended upon comparatively rigid spars as in the case of the sail shown in Fig. l but also in the case of other sails such as jibs and loose footed sails. In Fig. 8 is shown a `iib constructed to embody the improvement of this invention. The jib as shown is hoisted upon a wire or other luif line intended to be held under tension attached to the luff I5 extending from the tack I6 to the head I1. The jib is made up of a propulsive portion I8 formed of cloths sewn in conventional miter fashion. The lower edge of the propulsive portion I8 joins at a seam I9 with the upper edge of a camber forming portion 20.

The upper edge of the camber forming portion 20 of the sail shown in Fig. 8 conforms with the curvature of the trace formed by the intersection of the plane of the obliquely positioned camber forming portion 20 with the curved surface of the propulsive portion I8 when disposed in an aerodynamically effective contour. While in a jib or loose footed sail without the camber forming portion of this invention, the assumption of an aerodynamically advantageous curvature need not require distortion of the mesh of the canvas, such a sail, under wind action, tends to assume a nearly circular contour which is not favorable to an optimum propulsive effect. By providing the camber forming portion 20, the sail is encouraged to assume a desired contour, namely, one in which curvature is a maximum in the vicinity of the luif diminishing gradually as the leech is approached. In the case of a sail cut to set upon a gaif or in the case of a quadrilateral jib, a camber forming portion, both at the head and the foot of the sail, may advantageously be employed.

The sail construction of this invention may be looked upon as a means for providing draft in a sail Without need for curved margins intended to be hoisted or extended in straightened position. When thus regarded the invention resides in a particular form of internally cut draft in which a camber forming portion is provided by means of an arcuate seam such as seam 4 in Fig. 1 extending between two adjacent corners of the sail. This seam is curvilinearly darted from the point of highest curvature as at 2I in Fig 3 in opposite directions toward the corners of the sail standing at the ends of the seam. In doing so there is taken from the canvas of the sail when in at condition two curving and tapering darts as indicated at 22 and 23 to form what is herein termed a curvilinearly darted seam. By choice of the curvature of the seam and the degree oi darting, a sail may be provided with any shape of draft desired including a shape in which the sail may set under wind action Without distortion of the mesh of the canvas.

Herein the term distortion of mesh of the canvas is employed as meaning a condition imposed on the canvas under which the threads of warp and Woof cross one another at an angle other than the angle at which said threads are originally woven. The term canvas is employed herein as meaning cloth, film or sheet material of any kind employed to form the spread of a sail, and in the case of materials other than woven materials the term distortion of the mesh is intended to dene that rhomboidal deformation in the sheet or lm which results from shear acting within the sheet or lm.

I claim:

1. In an improved sail of the fore and aft type the combination comprising a propulsive portion adapted to assume a contour of aerodynamic advantage and a camber forming portion extending along a side of the sail other than the luff, said camber forming portion being disposed obliquely with respect to said propulsive portion at a pre-determined angle and having a curved edge joined to said propulsive portion the conguration of which curved edge conforms with the trace of intersection between the plane of the camber forming portion and the curved surface of said propulsive portion when disposed in said contour of aerodynamic advantage.

2. In an improved sail o the fore and aft type the combination comprising a propulsive upper portion adapted to assume a contour of aerodynamic advantage and a camber forming lower portion extending along the foot of the sail, said camber forming portion being disposed obliquely with respect to said propulsive portion at a predetermined angle and having a curved edge joined to said propulsive portion the configuration of which curved edge conforms with the trace of intersection between the plane of the camber forming portion and the curved surface of said propulsive portion when disposed in said contour of aerodynamic advantage.

3. In an improved sail of the fore and aft type the combination comprising a canvas propulsive portion having a head, a leech, a tack, a clew and a luff, said lui being adapted to be attached to a substantially rigid mast, said propulsive portion being adapted to be deformed under wind action without substantial distortion of the mesh of the canvas into a conical aerodynamic contour converging at the head the sections of which contour in a direction transverse to the luff conform with an aerofoil section, said propulsive portion having a curved lower edge of a curvature defined by the intersection with said propulsive portion when disposed in said aerodynamic contour of a plane disposed at a predetermined angle obliquely with respect thereto passing through said tack and clew, and a camber forming portion below said propulsive portion disposed in oblique relation to said propulsive portion at said predetermined angle having a foot adapted to be attached to a substantially rigid boom and a curved upper edge joined at a seam with said curved lower edge of said propulsive portion.

4. The combination with a sail of the fore and aft type having a head, a tack, a clew, a leech and a substantially straight lui and foot of draft forming means in the form of a camber forming portion extending along the foot of the sail formed by an arcuate seam starting at the tack extending rst aft and upwardly and thence aft and downwardly to said clew said seam being curvilinearly darted from the point of highest curvature forward to said tack and aft to said clew.

5. The combination with a sail of draft forming means in the form of a camber forming portion extending along one side of the sail formed by an arcuate seam springing from adjacent corners of the sail said seams being curvilinearly darted fro-m an intermediate point therein in both directions toward the ends thereof.

JAIWES A. MAURER. WALTER R. LINDEMANN.

No references cited. 

